//没看懂题目
#include <iostream>
using namespace std;
int main()
{
    int n;
    while(cin>>n)
    {
        if(n<=2)
            cout<<-1<<endl;
        else
        {
        	if(n%2==1)
                cout<<2<<endl;
            else if(n%4==2)
                cout<<4<<endl;
            else if(n%4==0)
                cout<<3<<endl;
        }
    }
    return 0;
}